diff options
| -rw-r--r-- | arch/x86/kernel/nmi.c | 35 |
1 files changed, 21 insertions, 14 deletions
diff --git a/arch/x86/kernel/nmi.c b/arch/x86/kernel/nmi.c index 2a07c9adc6a6..59ed74ec010e 100644 --- a/arch/x86/kernel/nmi.c +++ b/arch/x86/kernel/nmi.c @@ -359,17 +359,18 @@ static noinstr void default_do_nmi(struct pt_regs *regs) bool b2b = false; /* - * CPU-specific NMI must be processed before non-CPU-specific - * NMI, otherwise we may lose it, because the CPU-specific - * NMI can not be detected/processed on other CPUs. - */ - - /* - * Back-to-back NMIs are interesting because they can either - * be two NMI or more than two NMIs (any thing over two is dropped - * due to NMI being edge-triggered). If this is the second half - * of the back-to-back NMI, assume we dropped things and process - * more handlers. Otherwise reset the 'swallow' NMI behaviour + * Back-to-back NMIs are detected by comparing the RIP of the + * current NMI with that of the previous NMI. If it is the same, + * it is assumed that the CPU did not have a chance to jump back + * into a non-NMI context and execute code in between the two + * NMIs. + * + * They are interesting because even if there are more than two, + * only a maximum of two can be detected (anything over two is + * dropped due to NMI being edge-triggered). If this is the + * second half of the back-to-back NMI, assume we dropped things + * and process more handlers. Otherwise, reset the 'swallow' NMI + * behavior. */ if (regs->ip == __this_cpu_read(last_nmi_rip)) b2b = true; @@ -383,6 +384,11 @@ static noinstr void default_do_nmi(struct pt_regs *regs) if (microcode_nmi_handler_enabled() && microcode_nmi_handler()) goto out; + /* + * CPU-specific NMI must be processed before non-CPU-specific + * NMI, otherwise we may lose it, because the CPU-specific + * NMI can not be detected/processed on other CPUs. + */ handled = nmi_handle(NMI_LOCAL, regs); __this_cpu_add(nmi_stats.normal, handled); if (handled) { @@ -419,13 +425,14 @@ static noinstr void default_do_nmi(struct pt_regs *regs) pci_serr_error(reason, regs); else if (reason & NMI_REASON_IOCHK) io_check_error(reason, regs); -#ifdef CONFIG_X86_32 + /* * Reassert NMI in case it became active * meanwhile as it's edge-triggered: */ - reassert_nmi(); -#endif + if (IS_ENABLED(CONFIG_X86_32)) + reassert_nmi(); + __this_cpu_add(nmi_stats.external, 1); raw_spin_unlock(&nmi_reason_lock); goto out; |